Rotary encoders are used to measure rotary motions of a rotationally mounted element, especially a shaft, over one or more revolutions. In so doing, the rotary motion is recorded incrementally or absolutely. In conjunction with gear racks and gear wheels or with threaded spindles, a rotary encoder is also able to measure linear motions.
Rotary encoders are used in large numbers as so-called engine feedback devices and when used as such, form positional or angular information which is utilized for the commutation of electric drives. For example, in the case of synchronous motors, information about the absolute rotor position is required immediately after switching on the supply voltage. The rotary encoders with additional commutation signals, which supply relatively rough positional information, and the absolute rotary encoders in single-turn and multi-turn designs, which immediately output the exact angular position with an accuracy of a few angular seconds, are suitable for this purpose.
Such rotary encoders are often manufactured and installed in large quantities. Therefore, it is even more important that these devices can be produced in economical manner and are easy to assemble, e.g., on electric motors.
A rotary encoder which is able to be fixed in place by clamping in a hollow-cylindrical recess of an electric motor is described in European Patent No. 1 102 964.